Centrifugal fan and pump



' S. C. DAVIDSON.

CENTRIFUGAL FAN AND PUMP.

0N FILED DEC. 20. 1915. RENEWED M A AR. 18, I919- 1,363,959. Patented Dec. 28, 1920.

3 S EEEEEEEEEEE I- w ll S. C. DAVIDSON.

CENTRIFUGAL FAN AND PUMP. APPLICATION FILED mac. 20, I915. RENEWED MAR. 18,1919.

1,368,959. Patented Dec. 28,1920.

3 SHEETS-SHEET. 2-

S. C. DAVIDSON. CENTRI FUGAL FAN AND PUMP.

APPLICATION FILED DEC.20, I915- RENEWED MAR. I8, 1919.

1,363,959. Patented Dec. 28, 1920".

3 SHEETSQSHEET 3.

Q OOOOOOO OOOOOOO OOOOOOO SAMUEL CLELAND DAVEDSUN, 0E BELFAST, Ei-tELAND.

CENTEIFUGLEL FAN AND EJMP.

specification of Letters Patent.

Patented Dec. 28, 1&20.

Application filed December 20, 1915, Serial Ito. 67,802. Renewed March 18, 1919. Serial No. 283,438.

T 0 all whom it may concern:

Be it known that. I, SAMUEL CLnLANn Dnvmsox, a subject of th King of Great Britain and Ireland, residing at Sirocco Engineering -Works, Belfast, ireland, have invented certain new and useful Improvements in or Relating to Centrifugal Fans and Pumps, of which the following is a specification.

This invention relates to centrifugal fans or pumps (hereinafter referred to as fans) and has for its object to provide an in proved construction of that type of fan wherein an induced flow of air, water or other fluid (hereinafter referred to as air) is combined with he volume of air direct? discharged from the fan wheel.

The invention will be described in reference to a multibladed drum type of fan, but it is to be understood that it is applicable to other types of fan by suitable modifications.

According to this invention It combine with the centrifugal fan wheel an annular induction inlet or duct to direct Lne induced flow of air transversely or in an axial direction into the air which is being discharged directly from the fan wheel, the arrangement being such that the inner circumference of said annular induction inlet or duct terminates in an axial direction at or about the plane in which the nearest edge of the periphery of the fan wheel revolves. means being provided to prevent circumferential rotation of the air in said induction inlet or duct, without substantially obstructing the space immediately surrounding the periphery of the fan wheel.

As an example the induced air may be admitted to the space beyond the periphery of the centrifugal fan wheel through an annular opening the inner circumference of which is approximately of same diameter and adjacent to the peripheral edge of the fan wheel on the intake side thereof and adapted to direct the induced air transversely or in an axial direction into the air discharged directly from the fan wheel, and means for preventing circumferential rotation of the air in the said induction aperture or duct, may be provided in the form of guide plates or other suitable devices which do not to any substantial extent project at the inner edge of said annular induction inlet beyond the nearest peripheral edge of the fan wheel, that is to say that the peripheral annular space which is closely adjacent to the periphery of thefan wheel is so far free from obstruction that under the influence of the incoming induced flow of air the fan wheel when of multibladed drum shape with long axial and relatively narrow radial blades may become effectivefor the discharge of air through the whole or practically the whole of its axial length instead of being partly negative and partly positive, as referred to in a previous specification of Letters Patent granted to me and numbered 1,149,638, and others granted to me subsequently. Although the inner terminal end of said annular induction space and which is immediately adjacent to the periphery of the inte. re end of the fan wheel may be approximately coincident with the plane thereof its outer circumferential portion may be either in the same plane or more or less inclined to one or other side of said plane according to requirements and to the relative diameter of the annular induction opening employed to that of the fan wheel. The said annular induction inlet may be divided concentrically and may constitute the terminal ends of a series of concentric or radially arranged annular ducts, the air inlet ends of which may be arranged at different axial positions so as to prevent the suction effect on one inlet affecting the others. As a modification the area of the induction inlet and in some cases the primary inlet to the fan wheel itself may be divided into a multitude of small ducts or apertures arranged in the same plane or part in one plane and part in another, or may consist of a suitable foraminous web, perforated plate, .or a grid-like arrangement with or without means for regulating the admission of the induced air current.

The supply of primary air to the intake chamber of the fan wheel itself may be isolated from the innermost part of the annular induction space, and in some cases this primary air may be taken from a separate source which arran ement is articularl useful for fans which deal with hot furnace gases where the fan wheel itself may thus be supplied with relatively cool air from outside while the induction inlets deal with the hot furnace gases, which then pass into the discharge without passing through the fan wheel itself, thereby saving the fan wheel from the destructive effects of either excessively hot or corrosive gases.

The fan wheel may be inclosed in a suitable casing and the discharge therefrom may be either directly peripheral or merge into a spiral casing suitably disposed circumferentially or laterally.

I find with this invention when I employ a multi-blade drum shape of fan with axially long and radially narrow blades that air is discharged from the whole or practically the whole axial len th of the blades.

Further alaterally inclosed space may be provided beyond the diameter of the outermost induction duct for receiving the combined primary and induced air before same is discharged or passed outwardly into a suitable casing.

The accompanying drawings show some constructions of fan made in accordance with this invention.

Figure 1 is a section partly broken, Fig. 2 an elevation partly broken toward Fig. 1 from the left.

Fig. 3 is a section of a modified arrangement.

Fig. 4 is a vertical section showing a further modification.

Fig. 5 shows a modification of Fig. 4.

F ig. 6 shows a further modification combining the structures of Figs. 1 and 5.

Fig. 7 is a sectional elevation, and Fig. 8 a plan to illustrate the application of the invention for the purpose of exhausting hot furnace gases or corrosive gases.

Referring now to Figs. 1 and 2 I combine with a fan wheel a, of the drum shape (such as described in my prior Patent No. 1,149,638) an air duct or tube Z) hereinafter called the inner or main inlet or duct leading up to and terminating close to the intake end of the fan wheel a, said inner duct being of about the same diameter as the outer circumference of the said fan wheel. Outside the said inner or primary duct and concentric or substantially so therewith is a larger or intermediate induction duct 0 which terminates in an axial direction at the point 0' which is at or about the plane of the intake end of the fan wheel. The said duct 0 may, however, be extended inward over the fan wheel for a suitable distance and the annular air inlet space 2 between the inner primary duct and the intermediate larger duct 0 may be provided with guide plates (Z which may be disposed radially as shown or otherwise to prevent the and looking circumferential rotation of air in the said,

induction duct 2. Beyond the intermediate induction duct 2 is another or outer induction duct 8, the casing e of which is also carried in an axial direction over the plane of the intake end of the fan wheel for a suitable distance as shown, although if required it may extend only up to a point in the same plane as the point 0. At its termination the casing of the duct 6 is connected. to an annular plate 7 parallel with the plane of rotation of the fan wheel as shown, although it may be suitably inclined if required. The annular plate f together with a back plate 9 which extends radially and approximately parallel with the back of the fan wheel forms a circular casing with a peripheral opening of suitable width from which the whole volume of air both from the fan wheel and from the inner and outer induction ducts can freely discharge, and to render the discharge more positive a series of stationary guide plates it may be mounted in or around the periphery of the said circular discharge, as shown in Figs. 1, 2 and 3. The use of the said guide plates is optional and although they are an improvement, the apparatus works very well without them. In Figs. 4, 5 and 6 they are dispensed with. The guide plates 7a are shown as bent forward in the direction of rotation and the guide plates in the ducts 2 and 3 are shown as radial but they may be otherwise arranged.

In operation when the fan wheel a is being rotated the air will pass by the main inlet Z) into the fan wheel-and will be discharged therefrom into the space 0 and an induced current of air will flow inward through the inner and outer induction ducts 2 and 3 and will pass transversely or in an axial direc tion into the said air which is being discharged directly from the fan wheel a. The guide plates 7b prevent circumferential rotation of the air in the said induction ducts. The inner induction duct 0 terminates in an axial direction at or about the plane in which the nearest edge of the periphery of the fan wheel revolves, whereby the peripheral annular space which is closely adjacent to and immediately surrounds the periphery of the fan wheel is so far free from obstruction that under the influence of the incoming induced flow of air through the ducts 2 and 3 the fan wheel when of the multibladed drum shape with long axial and relatively narrow blades of the type shown, may become effective for the discharge of air through the Whole or practically the whole of its axial length instead of being partly negative and partly positive. With a fan of the construction herein described the total volume of air moved and dealt with is so much greater than the volume which actually passes through thefan wheel itself that a relatively small fan can be employed for the volume to be dealt with and which is a matter presentingv many important commercial advantages.

In the modified construction shown in v the termination of the inner main duct 7). erally into a tangential discharge of suitable The outer edge of the casing e is also set slightly farther back toward the fan wheel. With the exception that the corner between the casing e and the plate f is sharp instead of being rounded and apart from the above mentioned differences, the construction shown in Fig. 3 is similar to Figs. 1 and 2.

In a modified construction the outer or inner induction ducts may be provided with a large number of guide plates close together and subdivided concentrically so as to provide a multitude of small passages an equivalent of which may be provided by means of suitable perforated plates, or wire gauze or a metal grid of suitable depth may be substituted, with any of which modification means may be employed for regulating the amount of induced air admitted into the primary flow of air which has been discharged from the fan wheel.

Fig. 4 shows one such construction where a screen of wire mesh 5 covers the front of the fan wheel a and extends radially beyond the same to the point i where it is mounted in an annular plate 7 which corresponds with the plate f of Figs. 1 and 3. The back plates g remain as in the previous constructions.

Fig. 5 shows a modification of Fig. 4 wherein the wire mesh screen i is made with a central aperture of a diameter at or about the periphery of the fan wheel, while the outer edge is supported in a short cylindrical duct casing in.

Fig. 6 shows a construction wherein the inner duct Z) and 2 of Fig. 1 are employed with an outer annular inlet or duct 3 covered with wire gauze mesh 2', the construction being otherwise similar to Fig. 1.

Instead of the divisional screen i of wire gauze a screen of expanded metal or other suitable foraminous material may be em ployed, and the said divisional screen may be located either in or adjacent to the plane in which the intake end of the fan wheel rotates and either parallel therewith or conically inclined to one or other side thereof.

The operation of Figs. 4, 5 and 6 is similar in effect to that of Fig. 1 the screen of wire mesh operating in the same manner as the isolated ducts to effectively carry out the before mentioned flow of primary and induced air in large volume in an axial direction into the air which is discharged from the fan wheel itself.

If required the peripheral discharge from a casing such as described and illustrated may open into a spiral casing or inclosure disposed around or alongside the peripheral discharge which may merge thereinto by a suitable curve. Said spiral casing may in cross section be curved or rectangular and gradually enlarging either radially or latdimensions.

As an example, in Fig. 8, as hereinafter referred to, a casing a with; a tangential discharge therefrom into a spiral surrounding duct m m and thence into a chimney or discharge pipe is shown.

As shown in Figs. 7 and 8 the supply of primary air to the intake chamber of the fan wheel itself may be isolated from the innermost part of the annular induction spaces 2 and 3, the primary air being taken from a separate source by the pipe extension Z), while the induced air is taken from a space w. This arrangement is particularly useful for fans which deal with hot furnace gases of which the arrangement shown in Figs. 7 and 8 are examples, as it will be seen that the fan wheel itself is supplied with relatively cool air from outside by the pipe I) while the induction inlets 2 and 3 deal with the hot furnace gases from the fine 00, which hot furnace gases then pass into the discharge without passing through the fan wheel itself thereby saving the fan wheel from the destructive effects of either excessively hot or corrosive gases. In Fig. 7 a fan wheel and casing with peripheral discharge such as shown in Fig. 1 are illustrated, and in Fig. 8 the fan wheel a is shown as inclosed in a suitable casing a with a circumferential tangential discharge into the spiral casing marked m and m in Fig. 8 from which the gases are discharged into an uptake chimney which may be a continuation of m which is shown in plan. A wire screen 'i may be placed in front of the induction inlets 2 and 3, as shown in Fig. 7, if desired.

In the particular arrangement illustrated in Fig. 8 the line 00 is provided with a partition dividing the flue into two parts 00' m one passing through an economizer and the other forming a by-pass, suitable doors or valves 2 being provided whereby the furnace gases which are led to the fan may be passed through the economizer or through the bypass line as may be required.

IVithout illustration it will be obvious that the invention may be applied to a double intake fan i. 6., a fan wheel having an air inlet opening at its two opposite sides, in which case the inclosing casing or the like will be suitably modified and the center of the fan wheel or the casing beyond the periphery of the fan wheel may or may not be provided with a radially disposed annular dividing plate corresponding more or less with the mid-length of the fan wheel blades of the double fan wheel.

lVhat I claim and desire to secure by Letters Patent is 1. In centrifugal fans and pumps the combination of a centrifugal fan wheel having an inlet to center of wheel, an annular induction inlet of larger diameter than that of the fan wheel and terminating in an axial direction at or about the plane in which the nearest edge of the periphery of the fan wheel revolves, whereby the induced flow of air is directed transversely in an axial direction into the air being discharged directly from the fan wheel.

2. In centrifugal fans and pumps the combination of a centrifugal fan wheel having an inlet to center of fan wheel, an annular induction inlet of larger diameter than that of the fan Wheel and terminating in an axial direction at or about the plane in which the nearest edge of the periphery of the fan wheel revolves, whereby the induced flow of air is directed transversely in an axial direction into the air being discharged directly from the fan wheel, means being provided for preventing circumferential rotation of the air in said induction inlet without substantially obstructing the space immediately surrounding the periphery of the fan wheel.

3. In centrifugal fans and pumps the combination of a centrifugal fan wheel having an inlet to center of wheel, an annular induction inlet of larger diameter than that of the fan wheel and divided concentrically and terminating in an axial direction at or about the plane in which the nearest edge of the periphery of the fan wheel revolves, whereby the induced flow of air is directed transversely in an axial direction into the air being discharged directly from the fan wheel.

4. In centrifugal fans and pumps the combination of a centrifugal fan wheel having an inlet to center of wheel, an annular induction inlet of larger diameter than that of the fan wheel and divided concentrically and terminating in an axial direction at or about the plane in which the nearest edge of the periphery of the fan wheel revolves, whereby the induced flow of air is directed transversely in an axial direction into the air being discharged directly from the fan wheel, means being provided for preventing circumferential rotation of the air in the induction inlet without substantially obstructing the space immediately surrounding the periphery of the fan wheel.

5. In centrifugal fans and pumps the combination of a centrifugal fan wheel having an inlet to center of wheel, and an annular induction inlet of larger diameter than that of the fan wheel and terminating in an axial direction at or about the plane in which the nearest edge of the periphery of the fan wheel revolves, whereby the induced flow of air is directed transversely in an axial direction into the air being discharged directly from the fan wheel, and means for dividing said annular induction inlet into a number of similar inlets.

6. In centrifugal fans and pumps the combination of a centrifugal fan wheel having an inlet to center of fan wheel, an an nular induction inlet of larger diamter than that of the fan wheel and terminating in an axial direction at or about the plane in which the nearest edge of the periphery of the fan wheel revolves, whereby the induced flow of air is directed transversely in an axial direction into the air being discharged directly from the fan wheel, and means for covering said induction inlet with foraminous material.

7. In centrifugal fans and pumps the combination of a centrifugal fan wheel, a main inlet duct leading into said fan wheel, an annular induction duct concentric with and of larger diameter than said main inlet duct and terminating in an axial direction at or about the plane in which the nearest edge of the periphery of the fan wheel revolves whereby the induced flow of air is directed transversely in an axial direction into the air being discharged directly from the fan wheel, means whereby said main duct is supplied from a separate source to that of the induction inlet and whereby the fan may be adapted to deal with hot or corrosive gases which are led into the induction ducts while fresh or cool air is led into the fan wheel through the main inlet duct whereby the fan wheel is kept cool and is also protected from the destructive action of the hot or corrosive gases.

In witness whereof I have hereunto signed my name in the presence of two subscribing witnesses.

SAMUEL OLELAND DAVIDSON. lVitnesses HUGH TAYLOR CoUL'rER, IVILLIAM PEOPLES BLAcK. 

